1. Field of the Invention
The present invention relates generally to a lumbar support regulating apparatus in a seat back and more particularly to such an apparatus in a vehicle seat back.
2. Description of the Prior Art
In general, the use of a lumbar support regulating apparatus in the seat back of a motor vehicle seat is known so that the hardness of the cushion of the seat back which is in contact with the lumbar region of a person seated on the seat can be suitably regulated.
An example of such a construction is the U.S. Pat. to Sandor No. 3,378,299, granted Apr. 16, 1968 which uses pivoted lever members in the seat back. One arm of the lever engages the seat spring to vary the firmness thereof and the other arm of the lever is connected to a cable which may be wound up on a rotatable shaft to vary the force with which the lever is pressed against the seat spring.
Also known is the patent to Hayashi, U.S. Pat. No. 4,019,777, granted Apr. 26, 1977 wherein a torsion spring is wrapped about a vertically extending post secured to the frame of a seal back. One arm of the torsion lever is secured to a plate which is disposed in engagement with the seat springs and the opposite end of the torsion spring is engaged with a travelling nut threaded on a rotatable control shaft so that upon rotation of the shaft the force applied to the torsion spring will be varied to adjust the support pressure applied to the seat springs. Due to the axial movement of the nut on the control shaft, the post about which the torsion spring is wrapped must be offset a considerable distance from the axis of the control shaft thereby necessitating the use of a fairly thick seat back frame.